Shawn Zhang, a law student in Canada, has been using satellite imagery to identify potential camps throughout Xinjiang. Zhang, whose family in China have been contacted by police over his social media posts that were critical of Chinese leaders, including President Xi Jinping, has been using satellite imagery to track the sudden appearance of detention centers in Xinjiang - many of which are then used for reeducation purposes or have reeducation camps built nearby.

"Most Xinjiang cities are small. It is relatively easy to spot a detention center as it is very large, there are high thick concrete walls, watchtowers in the corners. And the recently built detention centers are likely located in the new suburbs rather than old city centers," Zhang told Business Insider.

Large parking lots, school-like buildings, and wire fences are also common with reeducation camps.

The largest building Zhang has found is in Dabancheng. After cross-referencing it with other reports, he estimates it holds 8,000 to 10,000 people. The latest available census figures from 2002 reported 40,000 people living in Dabancheng, a district of the Urumqi City, which indicates the center could hold 20% of this one area's population.